Frequency changer



Jan.9, 1940. w. R. KOCH 2,186,544

FREQUENCY CHANGER Filed April 23, 1957 3 Sheets-Sheet l E r n 3 t I Wtnfield R. X02 12 Gttorneg Jan. 9, 19.40. V w. R. KOCH- 2 186,5

FREQUENCY CHANGER Filed April 23, 1937 s Shets-Sheet s N L 1 N a W I Zinventor Winfield R.11"och g v (Iflorneg i atented jan. 9, i946 FREQUENCY CHANGER Winfield a. Koch, Merchantville, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application April 23, 1937, Serial No. 138,553

,(iClaims. (01. 250-36) This invention relates to frequency changers, and has for its principal object the provision of an improved frequency changer or divider and method of operation whereby the changing operation is accomplished substantially independently of irregularity in the input or control frequency;

The frequency changer of this invention is susceptible of being used for various purposes such as to control the operation of high speed counters, to prevent selective fading in radio receivers or the like. As applied to the control of high speed counters, it may include a number of similar frequency changer unitsconnected in cascade with one another. As applied to the prevention of fading in radio receivers, selective fading maybe controlled by adding the upper and lower side band frequenciesto obtain a signal of exactly twice carrier frequency, dividing this frequency by two by means of the device illustrated, and

may be used for various other purposes where it is desired to obtain frequency division which is substantially independent of irregularity in the input or control frequency.

The invention will be better understood from the following description whenconsidered in conznection with the accompanying drawings, and its scope is indicated by the appended claims.

Referring to the drawings: a

Figure 1 is a wiring diagram of one form of the improved frequency changer,

Figure 2 shows a number of explanatory curves relating to the operation of the device of Fig. 1,

Figure 3 is a wiring diagram of a modified form of frequency changer,

Figure 4 is a block diagram illustrating the application of the invention to a radio receiver, and

Figure 5 is a wiring diagram of the radio receiver illustrated by Fig. 4.

The frequency changer of Fig. 1 includes input terminals I ll to which may be supplied negatively polarized control impulses of one frequency, and a pair of output terminals I I from which may be derived alternating impulses of another frequency,

or a D. C. potential which changes with each cycle of operation. Between the terminals l U and 55 II are interposed an independent radio frequency oscillation generatorl2, a radio frequency amplifier l3, and a pair of sharp cut-off amplifiers l4 and l5 which have their input andoutputcircuits so interconnectedthat when current is supplied to one of the amplifiers the other is biased off in a manner which is comparable to multivibrator action. J

It will be observed that (1) the output circuit of the generator 12 is coupled to the input circuit of the amplifier I3 through a transformer 16, (2) the output circuit of the amplifier I3 is coupled through transformers l'land l8, respectively, to the input circuits of the devices I and i5, and (3) plate or anode current is supplied from a terminal l9 respectively through resistors 20 and 2| to the devices l4 and I5.

As will hereinafter appear in greater detail, the control grids of the devices 14 and I5 are subjected to three different potentials. Thus the control grid of the device I i issubjected (1) to an independent radio frequency potential applied through the transformer l'l, (2) to a direct current bias which is dependent on the plate current of the device l5 and is applied through a transformer 22, a detector 23 and a resistor 2 1, and (3) to a potential which is applied through a condenser 25 andjis dependent on the change in potential drop of the plate resistor 21. of the device l5. likewise the control grid of the device I5 is subjected to three potentials which are supplied respectively through the transformer It, through the associatedv transformer 26, rectifier 21 and resistor 28, and through a capacitor 29.

The impulses appearing in the various parts of the apparatus are illustrated by the curves of Fig. 2, wherein the curve A repr'esentslthe negative half of the impulses applied at the terminals Ill, the curve B represents the radio frequency impulses delivered at the. output of the 'amplifer 13, the curve C represents the potential drop of the resistor 2|, the curve D represents the potential drop of the resistor 20, and the curve E represents the impulses supplied at the terminals ll. 1 f i In the operation of the apparatus of Fig. 1, loadcurrent is transferred from one of the amplifiers [4 or 15 to the other on each application of a negatively polarized impulse to the input circuit of the amplifier I3. Thus, assumingthe device I4 to be carrying the load, the successive. steps of the operation are as follows: The amplified and rectified radio frequency impulses produce in theresistor 28 a potential'which biases the device [5 to cut-off. The radio frequency impulses are momentarily interrupted by a negative lobe of the control impulses. This reduces the potential drop of the resistor 28 and the device I5 starts to open. The potential drop of the resistor 2| operates through the capacitor 25 to increase the negative bias of device I4, thus reducing the potential drop of resistor 29 and causing a higher positive voltage to be applied to the capacitor 29, with operation similar to the well known multi-vibrator circuit. This action continues until the device i4 is biased to cut-off and the device i5 is wide open. Meanwhile, the negative impulse on amplifier l3 ceases, and the radio frequency is again present on the grids of amplifiers i l and iii. Because amplifier I5 is in operating condition, it amplifies the radio frequency which is then impressed on rectifier 23, and pro duces in resistor 24 a negative bias voltage for the grid of amplifier M, keeping it from becoming operative. When the radio frequency impulse is again momentarily interrupted by a negative lobe of the control impulse, the potential drop of the resistor it decreases and the device I4 starts to open. The potential drop of the resistor 20 increases and operates through the capacitor 29 to increase the negative bias of the device 15. This causes a decrease in the potential drop of the resistor 2!, thus making the grid of the device M more positive, and this action continues until the device I4 is wide open and the device I5 is biased to cut-01f. The return of the radio frequency locks the amplifiers in this state until the next applied negative impulse.

As indicated above, and as shown by the curves of Fig. 2, this method of operation has the advantage that irregularities or interruptions in the input or control impulses are exactly reproduced in the output impulses of the frequency changer.

The frequency changer of Fig. 3 differs from that of Fig. 1 in that the amplifiers it, i l and I5 are of the pentagrid type and the various control potentials are applied to separate grids instead of a single grid. The operation of this modification is similar to that of the arrangement of Fig. 1 and will be readily understood without further explanation.

Fig.4 illustrates the application of the invention to a radio receiver for reinforcing a carrier which is subject to selective fading or is otherwise suppressed. This receiver includes a radio frequency amplifier 3d, a first detector 3i, an intermediate frequency amplifier 32, a second detector 33, and an audio frequency amplifier 34. Associated with the detector 3! is the usual oscillation generator 35, and connected between the amplifier 32 and the detector 33 are a frequency doubler 36, an amplifier 37, a frequency changer 38, and an amplifier 39.

In the operation of the radio receiver of Fig. 4, the upper and lower side bands are added together by the frequency doubler 353 to produce impulses of a frequency twice that of the carrier. These double frequency impulses are selected and amplified by the device 3'! and are utilized by the frequency divider 38 to produce impulses of carrier frequency which are amplified by the amplifier 39 and supplied to the input circuit of the detector 33 to replace the carrier which has faded out. With the usual type of oscillating frequency divider, difficulty in the operation of this system is encountered for the reason that the short periods between words or the like, when no side bands are present, allow the oscillating frequency divider to drop out of step. Under these conditions, each group or series of side bands must pull the frequency changer back into step and objectionable distortion is produced. This difiiculty is avoided by the frequency changer of this invention for the reason that it does not oscillate during intervals when side bands are not present.

In the wiring diagram of Fig. 5, similar parts are indicated by the same reference numerals as those. applied to Figs. 1, 3 and 4, and the details of this figure will therefore be readily understood from the previous explanation. It will be noted that an additional intermediate frequency stage 453 has been included in the circuit of Fig. 5.

I claim as my invention:

1. The combination of a pair of electron discharge devices each provided with input and output circuits, means connecting each input on cuit to the other output circuit whereby oscillation takes place, means for applying a radio frequency control potential to said input circuits, and means including a rectifier connected between one of said output circuits and the other of said input circuits for applying to said input circuit a unidirectional potential which is dependent on the radio frequency current of said output circuit, whereby said oscillation is prevented so long as said control potential is applied.

2. The combination of a pair of electron discharge devices each provided with input and output circuits, means for applying an intermittent radio frequency control potential to said input circuits, means includingrectifiers connected between each of said output circuits and the other of said input circuits for applying to each input circuit a unidirectional potential which is dependent on the radio frequency current of the.

other output circuit, and means including capacitors connected between each output circuit and the other input circuit for applying to each input circuit a potential dependent on the change in average current in the other output circuit whereby oscillation takes place between said discharge devices when said radio frequency control potential is not applied.

3. In a device of the character described, the combination which includes a pair of electron discharge devices, means for causing said discharge devices to become alternately conductive, said means including a source of radio frequency currents, means for applying said radio frequency currents to said devices, means responsive to the radio frequency currents in said devices for maintaining one of said tubes in a non-conductive state, and means for momentarily interrupting the application of said radio frequency currents to said devices to cause theother of said discharge devices to become non-conductive.

4. In a device of the character described, the combination which includes a pair of electron discharge devices, means for causing said discharge devices to become alternately conductive, said means comprising a source of radio frequency currents, means for applying said radio frequency currents to said devices, means responsive to the radio frequency currents in one of said devices for maintaining the other of said devices in a non-conductive state, means for momentarily interrupting the application of said radio frequencyv currents to said devices to cause the other of said devices to become non-conductive, and means coupled to said devices for obtaining an output impulse whose amplitude varies in response to each successive interruption of said radio frequency currents.

5. In a device of the character described, the

- alternately conductive, said means comprising a source of radio frequency currents, means for applying said radio frequency currents to theinput circuits of said devices, means coupled to the output circuits of each of said devices for rectifying said radio frequency currents to obtain,

bias voltages the amplitudes of which are respectively determined by the state of conduction of the device to which said means is coupled, means for applying the bias voltage derived from each of said devices to the other of said-devices to maintain one of said devices in a non-conductive state, and means responsiveto a control impulse for interrupting the application of said radio frequency currentsto said devices to cause the other of said devices to become non-conductive.

, 6. The combination which includes a pair o electron discharge devices provided with input and output jelect'rodes, means for causing said deviceslto' become alternately conductive, said means comprising a source of radio frequency currents, means for applying said radiofrequency currents to the input electrodes of said devices,

means for applying" to the input electrode of each of said'de'vices a uni-directional blocking potential the amplitude of which is dependent upon the radio frequency current flowing to the output electrode of'the other of said devices, and means 'formomentarily interrupting the application of said radio frequency. currents to said devices to cause the blocking potential to be removed .from one tube and applied to the other;

WINFIELD R.- KOCH: 

